Effect Of Hardware Impairments Research Articles

Aerial intelligent reflecting surface for improving the secrecy performance of wireless systems with hardware impairments

SummaryIt has been confirmed that the aerial intelligent reflecting surface (AIRS) can dramatically improve the coverage and quality of service of wireless communication systems. This paper proposes to exploit an AIRS to enhance the physical layer security (PLS) of wireless communication systems. In particular, the AIRS flies at convenient positions for enhancing legitimate channel gain and reducing eavesdropping channel gain. Moreover, the worst‐case security is determined where the legitimate user is affected by hardware impairments (HIs) while the eavesdropper hardware is ideal (ID). The analytical expression of secrecy outage probability (SOP) of the considered systems (referred to as the AIRS‐HI systems) is derived over realistic Nakagami‐ channels recommended for application in the fifth and beyond generations (5G & B5G). To clarify the behaviors of the considered systems, the asymptotic expressions of signal‐to‐distortion‐plus‐noise ratio (SDNR) at the legitimate user, signal‐to‐noise ratio (SNR) at the eavesdropper, and SOP are also provided. Monte‐Carlo simulations are employed to confirm the accuracy of the derived theorem. Numerical results confirm that the SOP of the AIRS‐HI systems is dramatically higher than the SOP of the AIRS‐ID systems. In other words, a strong effect of HIs on the SOP of the AIRS‐HI systems is clearly indicated. Consequently, utilizing the high transmit power is not an effective solution to improve the secrecy performance of the AIRS‐HI systems. In contrast, it is essential to employ an appropriate transmit power tailored to the specific system parameters. Furthermore, the considerable advantages of incorporating AIRS are demonstrated through a comparison between the SOPs of AIRS‐HI systems and HI systems lacking AIRS. Additionally, a comprehensive examination of AIRS‐HI system behaviors is conducted by varying various system parameters, including the predefined secrecy rate, HI level, the number of reflecting elements (REs) in AIRS, WiFi network frequency, AIRS altitude, bandwidth, and channel fading order. These observations lead to the identification of numerous recommended solutions for enhancing the SOP performance of the considered AIRS‐HI systems.

Symbol error probability of mmWave communications with transmit antenna selection and RISs under the impacts of hardware impairments

SummaryIn practice, hardware impairments (HIs) often exist in wireless devices, especially in low‐cost device systems. However, previous reports usually ignored HIs due to the computational complexity in mathematical derivations, particularly in millimeter‐wave (mmWave) communications. This article proposes the usage of transmit antenna selection (TAS) and multiple reconfigurable intelligent surfaces (RISs) to address HIs in mmWave communications. In particular, TAS is utilized at the source to increase the received signal power at the destination and reduce the effects of HIs. Multiple channel gains from RISs are combined with the classical source‐destination channel gain at the destination. The symbol error probability (SEP) expression of the mmWave communications with TAS and RISs under the effects of HIs (shortened as the TAS‐RISs‐HIs communications) is formulated over Nakagami‐ channels and verified through Monte Carlo simulations. The effects of HIs on the SEP of TAS‐RISs‐HIs communications are demonstrated through numerical illustrations. Specifically, the SEP of the TAS‐RISs‐HIs communications is significantly higher than the SEP of the ideal hardware communications with TAS and RISs, especially in the high transmit power regime. As a result, ignoring HIs when evaluating the SEP of the mmWave communications can result in some inappropriate conclusions. Moreover, the joint and separate advantages of TAS and RISs are thoroughly analyzed when comparing the SEPs in the cases with and without TAS, with and without RISs.

The Effect of Hardware Impairments on the Error Bounds of Localization and Maximum Likelihood Estimation of mm-Wave MISO-OFDM Systems

This work investigates the localization process in milimeter-wave ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$mm$</tex-math></inline-formula> -Wave) multiple-input single-output (MISO) OFDM systems considering hardware impairments (HWIs) at both the base station (BS) and the mobile station (MS). The localization is performed on MS board by estimating the downlink channel parameters using a maximum likelihood (ML) estimator, and then transforming them to the localization parameters. Besides, the Fisher information matrix (FIM) is utilized to assess the accuracy of the estimation processes. The limits of the localization is calculated in terms of the position error bound (PEB). The obtained results of the computer simulations show the destructive impacts of the HWIs on the localization process with respect to the effective SNR, and the number of pilot transmissions, transmitter antennas and subcarriers.

Error Bounds for Localization in mmWave MIMO Systems: Effects of Hardware Impairments Considering Perfect and Imperfect Clock Synchronization

Localization demands high-accuracy positioning, and this rings especially true in the context of fifth-generation (5G) millimeter-wave (mmWave) systems. However, it is easier said than done. mmWave systems require a large number of antennas to be deployed at the transceiver, so having ideal hardware components at each antenna is unrealistic. Degradation in the received signal, caused by hardware impairments (HWIs), affects the spectral efficiency, which in turn influences user positioning. Moreover, a high level of clock synchronization between the base station (BS) and the user equipment (UE) is rarely achieved. In this article, we investigate the effect of HWIs on UE localization under synchronous and asynchronous conditions. In order to minimize imperfect synchronization, two anchors or two-way localization protocols, a round-trip (RLP) as well as a collaborative localization protocol (CLP) are used. Conducting the localization process using the BS, we find the position and orientation bounds. We then study the effect of HWIs on the error bounds under the mentioned scenarios. Our numerical results show that HWIs have a significant impact on localization in all conditions, localization using two anchors and the CLP being more robust, however, against HWIs. Based on our outcome, compensating for imperfect synchronization using RLP does not increase the resilience of the system against HWIs.

Error Bounds for 3D Localization and Maximum Likelihood Estimation of mm-Wave MISO OFDM Systems in the Presence of Hardware Impairments

Millimeter-wave ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$mm$ </tex-math></inline-formula> -wave) multiple-input single-output (MISO) systems are expected to be extremely advantageous for the fifth generation (5G) cellular systems. In fact, these systems are considered key enablers of centimeter-level localization accuracy, even in the case of a single base station (BS). However, there are still fundamental issues that need to be addressed when applying <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$mm$ </tex-math></inline-formula> -wave MISO systems to practical scenarios, namely the effects of hardware impairments (HWIs). In this study, the 3D localization accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$mm$ </tex-math></inline-formula> -wave MISO OFDM systems is investigated when there are HWIs at both the BS and the mobile station (MS). The localization is performed by estimating the downlink channel parameters of the line-of-sight (LOS) path using only a maximum likelihood (ML) estimator at the MS. We then transform these channel parameters into ones for localization. The Fisher information matrix (FIM) is employed to assess the accuracy of the estimation processes, considering also any non-LOS (NLOS) paths. The limit of localization is calculated in terms of the position error bound (PEB). Computer simulations demonstrate the destructive impacts of HWIs on the localization process. Moreover, it was proven that the effect of NLOS paths from unknown scatters on the localization process is related to the ratio between LOS and NLOS path gains.

Effects of Hardware Impairments on IRS-Enabled MISO Wireless Communication Systems

This letter considers an intelligent reflecting surface (IRS)-enabled multiple-input single-output (MISO) wireless communication system, where the direct link between the transmitter and receiver is assumed to be blocked. It assesses the effects of transceiver hardware impairments (HWI), IRS channels correlation and phase errors on the system performance. New accurate expressions for ergodic capacity, outage probability, average symbol error rate, and diversity order are derived. Numerical and simulation results show that the IRS channels correlation, phase errors and transceiver HWI adversely affect the system performance. It is also shown that transceiver HWI impose a finite limit on the ergodic capacity, which is irrespective of the number of IRS elements and transmit antennas, transmitted power, phase errors, spatial correlation, and fading conditions.

Error Analysis of the Joint Localization and Synchronization of RIS-Assisted mm-Wave MISO-OFDM Under the Effect of Hardware Impairments

This work investigates the theoretical bounds of the joint localization and synchronization processes in a reconfigurable intelligent surface (RIS)-assisted system. We address the case of millimeter-wave (mm-Wave) multiple-input single-output (MISO) orthogonal frequency-division multiplexing (OFDM) with non-ideal transceivers. Considering a single antenna mobile station MS aims to estimate the parameters of the downlinks from the base station (BS) and the RIS by observing a known sequence received by the MS directly from the BS and indirectly through the RIS. The theoretical bounds of the estimation process are assessed by using the Fisher information matrix (FIM). A transformation matrix is then used to convert the FIM of the downlink channel parameters to the FIM of the MS joint localization and synchronization parameters. Specifically, the transformation matrix is derived based on the geometric relationships that convert the estimated downlink channels’ parameters to the position coordinates and clock offset. Next, the Cramer-Rao lower bound (CRLB) matrix of the joint localization and synchronization process is obtained by using the pseudo-inverse of the FIM. Thus, the position error bound (PEB), as well as the synchronization error bound (SEB), are calculated. Computer simulation results are provided to illustrate the adverse effects of the HWIs on the accuracy of localization and synchronization. These results are given in proportion to the effective signal-to-noise ratio (SNR), the number of pilot transmissions, and the number of the RIS elements.

Secrecy outage analysis of satellite communication networks with hardware impairments and channel estimation errors

This Letter investigates the impacts of hardware impairments (HIs) and channel estimation errors (CEEs) on the secrecy performance of satellite communication networks with one legitimate user and one eavesdropper. Particularly, the authors derive the closed-form expression for the secrecy outage probability (SOP) of the considered secrecy satellite communication networks. Besides, in order to research the impact of the HIs and CEEs at high signal-to-noise ratios, they obtain the asymptotic expression for the SOP, which gives efficient and fast method to evaluate the effect of the considered system parameters on the secrecy system performance. At last, Monte Carlo computer results are given to verify the effects of HIs and CEEs on the secrecy system performance.

Impact of Hardware Impairments with Imperfect Channel Estimation for Cache-Enabled UAV Relaying Networks

The effects of hardware impairments with imperfect channel estimation for cache-enabled UAV networks are studied in this paper. The effects of the setup parameters, such as the number of cached or relaying nodes, the hardware impairment factor, the channel estimation error, and the transmission SNR, on the outage probability are present by deriving the exact closed-form expressions on outage probability. Also, the asymptotic results are present when the transmission SNR is large enough. From the asymptotic analysis, we can see that there is an error floor introduced by the hardware impairments and imperfect channel estimation. Specifically, the error floor is dependent on the channel estimation error factor, the hardware impairment distortion factor, and the QoS requirements. And the diversity order of the error floor for the cached/relaying links is equal to the number of cached/relaying UAV nodes.

Performance Analysis of Hybrid Satellite-Terrestrial Cooperative Networks With Relay Selection

This paper conducts the performance analysis of a hybrid satellite-terrestrial cooperative network (HSTCN) having multi-antenna terrestrial relays. By assuming the availability of the direct link between the satellite and the destination, and considering the effects of hardware impairments (HIs) and interference on both relays and destination, we first propose a relay selection scheme to enhance the quality of the downlink transmission of the considered HSTCN. Then, we derive analytical expressions for the outage probability (OP) and throughput of the system using the proposed relay selection scheme. Furthermore, the asymptotic behavior of the HSTCN at high signal-to-noise-ratio (SNR) is also investigated to reveal the diversity order and array gain of the system. Finally, computer simulation results are provided to show the effectiveness of the relay selection scheme. The analysis shows that the system performance is significantly affected by the HIs and interference.

Performance Analysis of Hardware-Impaired Overlay Cognitive Satellite–Terrestrial Networks With Adaptive Relaying Protocol

In this article, we consider an overlay cognitive hybrid satellite-terrestrial network consisting of a primary satellite source-receiver pair and a secondary transmitter-receiver pair on the ground while taking into account the practical hardware impairments (HIs) at the user devices. Herein, a secondary terrestrial user acts as a cooperative relay to assist the transmission of primary satellite user. In return for this kind of favor, the secondary user gets access to the primary's spectrum for its own communication. Further, we consider the distortion noises induced by all the hardware-impaired terrestrial nodes and demonstrate their detrimental impact on the system performance. We manifest analytically that, for the higher data rates, the HIs invoke ceiling effects which reprehensibly cap the fundamental capacity of the system. To mitigate the effect of HIs, we propose an adaptive relaying (AR) protocol for both amplify-and-forward and decode-and-forward operations and compare its performance with the competitive fixed relaying schemes. The proposed AR protocol efficiently utilizes the available degrees-of-freedom to enhance the system performance. We comprehensively analyze the overall system performance by deriving closed-form expressions for the outage probability of the primary and secondary networks under heterogeneous fading environments. Our theoretical developments are corroborated through various numerical and simulation results.

Performance analysis of non‐orthogonal multiple access based‐satellite communication networks with hardware impairments and channel estimations

This Letter investigates the impacts of hardware impairments (HIs) and channel estimation errors (CEEs) on the performance of non-orthogonal multiple access (NOMA)-based satellite communication networks. Especially, the authors obtain the closed-form expression of the outage probability (OP) of the considered NOMA-based satellite communication networks. Furthermore, in order to analyse the effects of HIs and CEEs in high signal-to-noise ratios (SNRs) regime, they derive the asymptotic expression of OP at high SNRs, which provide efficient and fast ways to evaluate the impact of system parameters on the system performance. In addition, Monte Carlo simulations are provided to verify the correctness of the analytical results.

Exploiting Impact of Hardware Impairments in NOMA: Adaptive Transmission Mode in FD/HD and Application in Internet-of-Things.

In this paper, a cooperative non-orthogonal multiple access (NOMA) system is studied for the Internet-of-Things (IoT) in which a master node intends to serve multiple client nodes. The adaptive transmission strategy is proposed at the relay node, i.e., the relay can be half-duplex (HD) and/or full duplex (FD). In practical terms, numerous low-cost devices are deployed in such IoT systems and it exhibits degraded performance due to hardware imperfections. In particular, the effects of hardware impairments in the NOMA users are investigated. Specifically, the closed-form expressions are derived for the outage probability. Moreover, the ergodic capacity is also analysed. This study also comparatively analyzes the orthogonal multiple access (OMA) and NOMA with HD and/or FD relaying. The numerical results are corroborated through Monte Carlo simulations.

Massive MIMO multi-pair two-way half-duplex AF FDD relaying: channel estimation

We consider two-way amplify-and-forward FDD massive multi-input-multi-output (MIMO) relaying system, where multiple half-duplex (HD) user-pairs exchange information via a shared HD relay equipped with massive MIMO. To design and study the performance of these systems, we require channel state information in uplink as well as in downlink. For the uplink of the system model, we use conventional low-complexity MMSE estimator for the channel estimation, wherein the number of orthogonal pilots required for uplink channel estimation are of the order of the number of users. However, in the massive MIMO relay systems, the downlink channel estimation becomes challenging, because of increased pilot overhead in proportion to the number of antennas at the relay and employing conventional channel estimation approaches will result in poor spectral efficiency. The massive MIMO channels exhibits sparse structure in the angular domain, due to limited scattering environment. We exploit this channel sparsity to reduce the pilot overhead by performing sparse Bayesian learning-based downlink channel estimation. Furthermore, practical massive MIMO systems are built with low-cost hardware components which makes the massive MIMO system prone to hardware impairments like phase and quantization errors. In this paper, we numerically analyze the effect of hardware impairments on the two-way multi-pair half-duplex massive MIMO relay systems.

Outage Analysis of Non-Orthogonal Multiple Access-Based Integrated Satellite-Terrestrial Relay Networks With Hardware Impairments

In this article, we investigate the impact of hardware impairments (HIs) on the performance of non-orthogonal multiple access (NOMA) based integrated satellite-terrestrial relay networks (ISTRNs). Particularly, we obtain the novel closed-form expression for the outage probability (OP) of the considered NOMA-based ISTRNs with HIs. Furthermore, to get further insights of the effect of HIs on the considered system in high signal-to-noise ratios (SNRs) scenario, the asymptotic expression for the OP is also obtained, which provides an efficient way to evaluate the system performance, and effective quantification of different parameters on the system performance. Furthermore, we study the energy efficiency (EE) of the considered system and obtain interesting findings when NOMA scheme is applied. At last, numerical Monte Carlo (MC) results are given to verify the correctness of the theoretical results.

Performance Analysis of Two-Way Satellite Terrestrial Relay Networks With Hardware Impairments

In this letter, the effect of hardware impairments on two-way satellite-terrestrial hybrid relay networks is analyzed. The terrestrial relay is considered as a two-way relay, which can transmit signals to both the satellite source and the mobile source simultaneously. Specifically, the closed-form expression, the asymptotic expression at high signal-to-noise rates and the throughput for the considered system are derived. The expressions show that the impairments greatly affect the system performance and system performance will be worse when the impairment level is larger. In addition, numerical results are provided to show the correctness of the analytical results.

Massive MIMO full-duplex relaying with hardware impairments

Massive multiple-input-multiple-output full-duplex relaying (MM-FDR), which exploits both the benefits of large-scale antenna arrays and full-duplex transmission, is considered as a promising technology to achieve very high spectral efficiency in the future wireless network. Despite the inevitable presence of transceiver impairments due to the use of low-cost hardware components, most of the prior works on MM-FDR assume perfect transceiver hardware which is unrealistic in practice. This paper investigates the impact of hardware impairments on the MM-FDR. Based on the recent experimental results, the effect of hardware impairments is modeled using transmit and receive distortion noises. The end-to-end achievable rate is derived and the scaling behaviors of echo interference due to the full-duplex operation, multi-user interference and effective distortions caused by hardware impairments are obtained. The scaling results show that the achievable rate of MM-FDR is limited by the hardware impairments at the sources and destinations, instead of that at the relay or other interferences, as the number of relay antenna tends to infinity. A low-complexity power control scheme is proposed to further improve the energy efficiency of MM-FDR with hardware impairments. Simulation results show that the proposed scheme can improve the spectral-energy efficiency tradeoff significantly.

Performance analysis of relay‐assisted CoMP transmissions with non‐ideal transceiver

Coordinated multi-point (CoMP) transmission is a promising technique for improving spectral efficiency and overall system throughput in future cellular communication systems. This study investigates the downlink performance of relay-assisted CoMP transmissions. The non-ideal transceiver scenario that considers the effects of hardware impairments on the performance of CoMP transmission is presented. The performance of relay-assisted CoMP transmission using a hybrid opportunistic cooperative (HOC) protocol is evaluated and compared for two different CoMP transmission strategies: coordinated beam-forming and joint processing (JP). For each strategy, the performance in terms of outage probability, average sum rate and throughput is studied. The non-COMP strategy is also included for comparison. Both theoretical and simulation results are considered to test the performance of ideal and practical scenarios of both CoMP transmission using HOC protocol and other relaying protocols such as amplify-and-forward (AF) and decode-and-forward (DF) protocols. The obtained results show that the HOC protocol with ideal scenario, significantly improves the average sum rate, the net throughput and the outage probability of CoMP transmission especially when considering the JP strategy. The obtained results also indicate that, the performance degradation due to non-ideal transceiver with HOC protocol is small when compared with AF and DF protocols.

Multipair two-way massive MIMO AF relaying with ZFR/ZFT and hardware impairments over high-altitude platforms

HAPs (High-Altitude Platforms) are one of the most promising alternative infrastructures for providing wireless communications to overcome the shortcomings of terrestrial-tower-based and satellite systems. This paper investigates a multipair two-way MM-AF (Massive MIMO Amplify-and-Forward) relay system over HAPs, where multiple user pairs exchange information within a pair through a relay with a very large number of antennas, and a HAP channel is modeled to follow a Rician fading distribution because of the presence of a line-of-sight path. First, the effect of hardware impairments on a multipair two-way MM-AF system is taken into consideration and is modeled using transmit and receive distortion noises. Then, ZFR/ZFT (Zero-Forcing Reception/Zero-Forcing Transmission) processing matrices of HDR (Half-Duplex Relaying) and FDR (Full-Duplex Relaying) with imperfect channel state information are presented. Finally, the asymptotic expressions of an end-to-end SINR are derived. Theoretical analyses and simulation results show that when the number of relay antennas grows very large, the SE (Spectral Efficiency) of an MM-AF relay system is limited by hardware impairments at the users instead of those at the relay, or by other types of interference. Thus, the quality of the hardware at a relay can be decreased without significantly degrading performance.

Hardware Impairments Aware Transceiver for Full-Duplex Massive MIMO Relaying

This paper studies the massive MIMO full-duplex relaying (MM-FDR), where multiple source-destination pairs communicate simultaneously with the help of a common full-duplex relay equipped with very large antenna arrays. Different from the traditional MM-FDR protocol, a general model where sources/destinations are allowed to equip with multiple antennas is considered. In contrast to the conventional MIMO system, massive MIMO must be built with low-cost components which are prone to hardware impairments. In this paper, the effect of hardware impairments is taken into consideration, and is modeled using transmit/receive distortion noises. We propose a low complexity hardware impairments aware transceiver scheme (named as HIA scheme) to mitigate the distortion noises by exploiting the statistical knowledge of channels and antenna arrays at sources and destinations. A joint degree of freedom and power optimization algorithm is presented to further optimize the spectral efficiency of HIA based MM-FDR. The results show that the HIA scheme can mitigate the "ceiling effect" appears in traditional MM-FDR protocol, if the numbers of antennas at sources and destinations can scale with that at the relay.